Modern central heating systems, and especially pressurised/sealed central heating systems, require treatment with anti-freeze, rust inhibitor chemicals and/or descaling or limescale inhibiting chemicals or other chemicals on a regular basis to ensure good maintenance of the system. In general this is done by service engineers/plumbers who carry out regular site visits to premises with such systems. The specialized nature of the task when dealing with pressurised/sealed central heating systems has lead to development of specialized apparatus and procedures for the purpose and there are a number of relevant patents.
Addition of rust inhibitor chemicals to non-pressurised systems is the subject of patent applications and patents from twenty years ago and earlier, as exemplified by UK patent GB 2162164B and its citations. GB 2162164B concerns use of a sealed vessel to receive the rust inhibitor. A volume of water is added into the vessel as diluent/flushing medium. The vessel has an inlet for pressurised air from a separate pump such as a bicycle pump to drive the chemical-laden fluid into a radiator of the non-pressurised central heating system via a bleed valve of the radiator. This approach introduces air into the system but this is not a major problem for the non-pressurised system since the air can simply be bled back out subsequently. The process is relatively risk-free and can be carried out by a home-owner. It does not need to be done by a professional.
When dealing with a pressurised central heating system the process is made substantially more difficult by the very fact of pressurization. Some have sought to address the problem by introducing the dosing vessel into the circuit of the pressurised central heating system between the cold water supply pipe and central heating return pipe of the system so that the inflowing cold water swirls in the vessel and carries the chemical up from the floor of the vessel into the central heating system. An example of this is disclosed in UK patent application G62442008A where a pair of hoses is provided one to couple the vessel to the cold water supply pipe and the other to couple the vessel to the central heating return pipe.
The arrangement in GE42442008A enables dosing to be carried out relatively safely since the hoses are coupled in place and valves to the hoses are only opened when the circuit through the vessel is water-tight. However, the delivery of the water and chemicals is inefficient and relies on a sufficient flow of water to have passed through the vessel to transfer substantially the whole dose of chemical into the system before the vessel and hoses can be uncoupled from the system. This may entail twenty or more liters of water having to pass through a liter-sized vessel before the plumber/service-engineer can be reasonably sure that all of the chemical has been substantially fully passed/flushed into the system. For a plumber/service-engineer on the clock this can be a significant waste of his time (and the client's money). Furthermore, this can be wasteful of water and incur extra water meterage charges for the customer.
It is a first object of the present invention to provide an improved method and apparatus for dosing a fluid/water system such as, for example, a central heating system, or a medical drip or any other flow system with one or more chemicals/treatment fluid and which allows rapid and substantially accurate dosing with minimal usage of water/fluid to flush the chemicals/treatment fluid into the system.
A further set of problems arise with regard to piston-operated devices for dispensing fluids, and especially dosing or administering two or more doses of the same or different materials at least one of which is fluid (the materials may both be fluid or be one liquid and the other a solid soluble or transportable in the fluid) materials which should be unmixed/kept apart prior to or during delivery. Such devices may include syringes for delivery of multiple medicaments or even for drinks that are to be dispensed in shots, and cartridges for mastic guns or other plunger devices. Existing syringes that deliver multiple materials generally do so in parallel or provide little control over mixing of the materials and generally fail to provide an effective way of dispensing two materials sequentially with a single plunger or in a staged controlled manner.
It is thus a further object of the present invention to address these latter problems and provide improved piston-operated devices such as syringes or cartridges for mastic guns or other plunger devices that allow two or more materials to be delivered sequentially or in a staged manner.